PLC chip junction device using an optical sensor

ABSTRACT

Disclosed is a junction device for assembling a PLC (Planar Lightwave Circuit) chip and an optical-fiber block used in an optical-communication system. The junction device includes: an ultraviolet-hardening adhesive filled into a space between the interfaces of the PLC chip and the optical-fiber block, the interfaces being inclined at a given angle; an ultraviolet-light source positioned over the ultraviolet-hardening adhesive for hardening the ultraviolet-hardening adhesive; an optical sensor positioned under the ultraviolet-hardening adhesive for measuring the power changes in the ultraviolet output that have penetrated through the ultraviolet-hardening adhesive; an optical power-meter for displaying the power changes of the ultraviolet based on the data received from the optical sensor; and, a controller for detecting when the ultraviolet-hardening adhesive is completely hardened based on data received from the optical power-meter.

CLAIM OF PRIORITY

[0001] This application makes reference to and claims all benefitsaccruing under 35 U.S.C. Section 119 from an application entitled, “PLCChip Junction Device Using an Optical Sensor,” filed in the KoreanIndustrial Property Office on Jul. 6, 2001 and there duly assigned Ser.No. 2001-40255.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention generally relates to a PLC (PlanarLightwave Circuit) chip and, in particular, to an electricalinter-connection of the PLC chip and electrical components on anintegrated package.

[0004] 2. Description of the Related Art

[0005] A WDM (Wavelength Division Multiplexing) communication system istypically used in transmitting a large amount of data, in which aplurality of optical signals having N wavelengths is simultaneouslytransmitted through a strand of optical fiber. In order to convert theoptical signals received into corresponding electrical signals thereceived optical signals are separated according to their respectivewavelengths prior to the conversion process. In a WDM communicationsystem employing a single-mode optical fiber an AWG (Arrayed WaveguideGrating) is widely employed to separate the received optical signalsinto multiple wavelengths.

[0006] Recently, many research efforts have been concentrated on findingan optimal way of integrating an optical waveguide device on a planarsubstrate using a PLC for many of the optical-signal processing, such asoptical-signal dividing, modulation, switching, and multiplexing.Techniques necessary for manufacturing the integrated optical waveguidedevice include waveguide designing, manufacturing, and packaging. Theoptical waveguide serves as an optical transmission line, which confinesan input light and propagates the input light with low signal loss. Theoptical waveguide comprises a core having a high refractive index and acladding having a low refractive index and surrounding the core. Theoptical waveguide device is manufactured, for example, through theprocess of depositing multi-layered thin silica or polymer films on asilicon or quartz substrate. By using the difference in the refractiveindices between the core and the cladding, the optical waveguide devicedivides light, changes the light path, and controls the light strength.

[0007]FIG. 1 illustrates an array of structures of a PLC chip accordingto the prior art. For simplicity, an adhesive is not shown in FIG. 1. Asshown in FIG. 1, a PLC chip 10 is connected to the optical fibers F1 (asingle optical fiber) and F2 (a ribbon optical fiber) through the I/Oparts of the optical-fiber blocks 12 and 14, respectively. The PLC chip10 and the optical-fiber blocks 12 and 14 are aligned in a straightline, and the arrayed arrangement is fixed using an adhesive. In orderto feed light into the PLC chip 10 and receive light from the PLC chip10, the optical-fiber blocks 12 and 14 are positioned and aligned withthe I/O ports of the PLC chip 10 in a straight line.

[0008] The function of the optical-fiber blocks 12 and 14 is to supportthe optical fibers F1 and F2. The optical-fiber block is manufactured byforming a V-shaped groove on a silicon substrate, placing an opticalfiber in the V-shaped groove, and fixing the optical fiber thereon usingan adhesive (or an epoxy resin). In addition, glass plates G1 and G2 areprovided to the upper surface of the PLC chip 10, and PYREX™ glassplates G3 and G4 are respectively attached to the upper surface of theoptical blocks 12 and 14 to hold the optical fibers F1 and F2 in place.Note that the interfaces 10 a, 10 b, 12 a and 14 a between the PLC chip10 and the optical blocks 12 and 14 are sloped at a specific angle. FIG.2 illustrates the interfaces 10 a, 10 b, 12 a, and 14 a inclined at anangle θ of about 8 degrees relative to the vertical line L so as toreduce the light loss caused by the reflection of light as the lightpropagates there-through.

[0009] With a continued reference to FIG. 2, a description will be madeof a conventional junction method, in which the PLC chip and theoptical-fiber blocks assembled as shown in FIG. 1 are joined togetherusing an ultraviolet-light source 16 and an adhesive B. In particular,FIG. 2 shows a conventional junction structure between the PLC chip 10and the optical-fiber block 14.

[0010] After aligning the PLC chip 10 and the optical-fiber block 14 ina line, the adhesive B (preferably, an ultraviolet-hardening resin) isapplied to the interfaces 10 b and 14 a and later becomes hardened. Thehardening process is performed by applying ultraviolet rays to theapplied adhesive for a given time using the ultraviolet-light source 16,thereby fixing the arrayed state. That is, in the conventional junctionmethod, after the adhesive is applied to the interfaces, the appliedadhesive is hardened using the ultraviolet-light source 16. A Lens 18provided to the ultra-violet source 16 guides the ultraviolet raysirradiated by the ultraviolet-light source 16.

[0011] However, as the ultraviolet-light source 16 is positioned overthe inclined interfaces 10 b and 14 a in the conventional method, theultraviolet rays 16 a irradiated by the ultraviolet-light source 16 andguided by the lens 18 are diagonally applied to the adhesive B disposedbetween the inclined interfaces. As such, the lower part of the appliedadhesive B does not become hardened properly, while the upper part ofthe applied adhesive B is well hardened. This is because the ultravioletrays 16 a cannot penetrate the lower part of the applied adhesive B dueto the inclined interfaces, which in turn cause an undesirable twistphenomenon in the junction structure during the subsequent processes,thereby deteriorating the reliability of an optical device.

SUMMARY OF THE INVENTION

[0012] The present invention is directed to a junction device forefficiently hardening the adhesive applied to interfaces between a PLCchip and an optical-fiber block.

[0013] One aspect of the invention is to provide a junction device foraccurately detecting the time when the applied adhesive is completelyhardened by measuring changes in the ultraviolet transmissiveness of anadhesive material.

[0014] Accordingly, there is provided a junction device for arraying aPLC chip and an optical-fiber block and fixing the arrayed state. Thejunction device includes: an ultraviolet-hardening adhesive filled intoa space between the interfaces of the PLC chip and the optical-fiberblock, the interfaces being inclined at a given angle relative to avertical line; an ultraviolet-light source positioned over theultraviolet-hardening adhesive for hardening the ultraviolet-hardeningadhesive; an optical sensor positioned under the ultraviolet-hardeningadhesive for measuring changes in the ultraviolet power that haspenetrated the ultraviolet-hardening adhesive; an optical power-meterfor displaying the power changes in the ultraviolet using data receivedfrom the optical sensor; and, a controller for detecting the time whenthe ultraviolet-hardening adhesive is completely hardened based on thedata received from the optical power-meter.

[0015] According to another aspect of the invention, a method ofassembling a PLC (Planar Lightwave Circuit) module is provided. Themethod includes the steps of: providing an optical/electrical devicehaving a PLC (Planar Lightwave Circuit) chip and an optical-fiber block,the contacting surface between the PLC chip and the optical-fiber blockhaving an inclined contact area at a predetermined angle; providing anadhesive material between the contact area of the PLC chip and theoptical-fiber block; applying an ultraviolet ray to the adhesivematerial at the predetermined angle to harden the adhesive material;and, monitoring a change in the ultraviolet ray output that haspenetrated the adhesive material in a substantially vertical direction.The method further includes the step of stopping the ultraviolet ray tothe adhesive material when there is no change in the ultraviolet-rayoutput.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other features and advantages of the presentinvention will become more apparent from the following detaileddescription when taken in conjunction with the accompanying drawings inwhich:

[0017]FIG. 1 is a perspective view of a PLC chip and the I/O parts'optical-fiber blocks, which are arrayed according to the conventionalart;

[0018]FIG. 2 is a schematic diagram illustrating a conventional methodof applying an adhesive to the interfaces between the PLC chip and theoutput part of the optical-fiber block and hardening the adhesive to fixthe arrayed state; and,

[0019]FIG. 3 is a schematic diagram illustrating a junction device andits related method for applying an adhesive to the interfaces betweenthe PLC chip and the optical-fiber block and hardening the adhesive tofix the arrayed state according to a preferred embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0020] In the following description, for purposes of explanation ratherthan limitation, specific details are set forth such as the particulararchitecture, interfaces, techniques, etc., in order to provide athorough understanding of the present invention. However, it will beapparent to those skilled in the art that the present invention may bepracticed in other embodiments, which depart from these specificdetails. For purposes of simplicity and clarity, detailed descriptionsof well-known devices, circuits, and methods are omitted so as not toobscure the description of the present invention with unnecessarydetail. It should be noted that an optical-fiber-block assemblymentioned in this disclosure indicates an optical-fiber block with acover.

[0021]FIG. 3 illustrates the structure of a junction device for applyingthe adhesive to the interfaces between the arrayed PLC chip andoptical-fiber block to be hardened by an ultraviolet source according tothe preferred embodiment of the present invention.

[0022] As shown in FIG. 3, the junction device according to thepreferred embodiment of the present invention is capable of joining thePLC chip 10 and the optical-fiber block 14 in a precise manner. The PLCchip 10 is manufactured through a known process of depositingmulti-layered thin silica or polymer films on a planar silicon wafer W.Due to the difference in the refractive indices between a core and acladding surrounding the core, an optical signal can be propagatedthrough a waveguide of the PLC chip 10. The PLC chip 10 and theoptical-fiber block 14 are arrayed in a line and then fixedly joinedtogether. Although FIG. 3 shows only the junction structure between thePLC chip 10 and the optical-fiber block 14, the junction structure alsocan be applied to joining the PLC chip 10 and the optical-fiber block12. Thus, the drawing should not impose a limitation on the scope of thepresent invention. Note that the arrayed PLC chip 10 and optical-fiberblock 14 are packed into a housing (not shown) later as anoptical-communication module.

[0023] The PLC chip 10 multiplexes/demultiplexes, divides, modulates, orswitches propagating signals therethrough according to the waveguidedesigned on the silicon wafer W. The glass plates G1 and G2 arerespectively attached to the I/O parts of the silicon wafer W so as tofacilitate a manufacturing process. It should be noted that the PLC chip10 is well known by those skilled in the art, thus a detaileddescription of the PLC chip 10 is omitted.

[0024] The optical-fiber block 14 includes a V-shaped groove (not shown)for receiving the optical fiber F2. To this end, the optical-fiber block14 is used to couple the optical fiber F2 and the output port of thewaveguide of the PLC chip 10. In addition, the PYREX™ glass plate G4 isattached to the top of the optical-fiber block 14 to hold the opticalfiber F2 positioned on the V-shaped groove.

[0025] The interfaces 10 b and 14 a between the PLC chip 10 and theoptical blocks 14 are sloped at a given angle relative to the verticalline, L. Specifically, the interfaces 10 b and 14 a are inclined at aslope angle θ of about 8 degrees to the vertical line L so as to reducethe light loss due to the reflection of light during the propagationstage. To fixedly hold the PLC chip 10 and the optical-fiber block 14 ina straight line, an adhesive B (specifically, an ultraviolet-hardeningresin) is filled into a space between the interfaces 10 b and 14 a, thenhardened using an ultraviolet light source 20. The present inventionfurther provides a process of precisely measuring the power ofultraviolet rays 20 b in real time during the hardening process so as toperform precisely the hardening operation. To this end, the junctiondevice includes the ultraviolet-light source 20 positioned over theapplied adhesive B and an ultraviolet-power measuring means(specifically, an optical sensor 28) positioned under the appliedadhesive B to measure in real time the changes in the power of theultraviolet rays 20 b that have penetrated the applied adhesive B duringthe hardening process.

[0026] In the embodiment, the ultraviolet-light source 20 includes alens 22 for transmitting the ultraviolet rays irradiated by theultraviolet-light source 20 to the applied adhesive B. As the lens 22and the applied adhesive B are arrayed in a straight line, ultravioletrays 20 a penetrating the lens 20 can be applied to the applied adhesiveB in a straight path, thus uniformly passing through the adhesive. As aresult, the straight traveling of the ultraviolet rays 20 a through theadhesive B minimize the loss due to the reflection of the ultravioletrays 20 a as in the prior art system.

[0027] The optical sensor 28 measures the changes in the output power ofthe ultraviolet rays 20 b that have penetrated the applied adhesive B,then provides the measured data to an optical power-meter 24. Theoptical power-meter 24 displays the measured data provided from theoptical sensor 28 and provides the measured data to a controller 26. Thecontroller 26 detects when the applied adhesive B is completely hardenedusing the measured data. As the hardening process progresses, the lighttransmissiveness of the applied adhesive B changes. In general, thelight transmissiveness increases or decreases according to thehardening-operation progress. After the applied adhesive B is completelyhardened, the strength of light penetrating the completely hardenedadhesive B does not change anymore. Therefore, the junction deviceaccording to the present invention can find out the time when theapplied adhesive B is completely hardened, by measuring the strength ofthe light penetrating the applied adhesive during the progress of thehardening process.

[0028] A description will be made now of the hardening process accordingto the present invention. After the ultraviolet-light source 20 and thelens 22 are arrayed so that the strength of the ultraviolet rays 20 bcan be maximized, the adhesive B that can be hardened by an ultravioletis filled into the space between the interfaces 10 b and 14 a. When theadhesive B penetrates evenly into the space, the ultraviolet-lightsource 20 is turned on. The strength of the ultraviolet rays 20 b ismeasured using the optical sensor 28. As the hardening processprogresses, the strength of the ultraviolet rays 20 b varies. After alapse of a given time, the strength of the ultraviolet rays 20 b doesnot vary anymore. At this time, the hardening process ends.

[0029] As described above, the present invention can array optimally theultraviolet-light source and the adhesive applied to the interfacesbetween the PLC chip and the optical-fiber block, then precisely findout the point when the applied adhesive is completely hardened bymeasuring the strength of the ultraviolet rays that have penetrated theapplied adhesive using the optical sensor positioned under the appliedadhesive. As a result, the present invention can reduce the wholehardening process and increase reliability on the optical device.

[0030] While the invention has been shown and described with referenceto a certain preferred embodiment thereof, it will be understood bythose skilled in the art that various changes in form and detail may bemade therein without departing from the spirit and scope of theinvention as defined by the appended claims.

What is claimed is:
 1. A junction device for assembling a PLC (PlanarLightwave Circuit) chip and an optical-fiber block, comprising: anadhesive material disposed between the PLC chip and the optical-fiberblock, the PLC chip and the optical-fiber block having an inclinedsurface area at a predetermined angle; an ultraviolet-light sourcepositioned over the ultraviolet-hardening adhesive for providing anultraviolet ray to harden the adhesive material; an optical sensorpositioned under the ultraviolet-hardening adhesive for measuring apower change of the ultraviolet ray that has penetrated the adhesivematerial; an optical power-meter for displaying the power change in theultraviolet ray based on the output from the optical sensor; and, acontroller for detecting when the adhesive material is completelyhardened based on the output from the optical power-meter.
 2. The deviceas claimed in claim 1, wherein the ultraviolet-light source and theadhesive material are arrayed so that ultraviolet ray radiated by theultraviolet-light source can be applied to the adhesive material in asubstantially straight path.
 3. The device as claimed in claim 1,wherein the optical sensor and the adhesive material are arrayed in asubstantially straight line so that the optical sensor can measure thepower change of the ultraviolet ray outputted through the adhesivematerial.
 4. A method for assembling a PLC (Planar Lightwave Circuit)module, the method comprising the steps of: providing anoptical/electrical device having a PLC (Planar Lightwave Circuit) chipand an optical-fiber block, the contacting surface between the PLC chipand the optical-fiber block having an inclined contact area at apredetermined angle; providing an adhesive material between the contactarea of the PLC chip and the optical-fiber block; applying anultraviolet ray to the adhesive material at the predetermined angle toharden the adhesive material; and, monitoring a change in theultraviolet-ray output that has penetrated the adhesive material in asubstantially vertical direction.
 5. The method of claim 4, furthercomprising the step of stopping the ultraviolet ray to the adhesivematerial when there is no change in the ultraviolet-ray output.